Illuminated electronic time piece



March 5, 1963 J. A. HuLTQUls'r 3,079,748

ILLUMINATED ELECTRONIC I TIME PIECE Filed June 27. 19Go INVENToR J- LBERT lll/L T01/IST BY @af/Wi ATTORNEY 3,079,748 ILLUMINATED ELECTRONIC TME PIECE I. Albert Hultquist, Scarsdale, NSY., assigner to Sylvania Electric Products Ine., a corporation of Delaware Filed `lune 27, 1960, Ser. No. 38,836 Claims. (Cl. S--Si The present invention relates to portable time pieces such as traveling clocks, pocket watches and wrist watches and, more particularly, to an arrangement for facilitating the reading of time at night, particularly when no external source of illumination is available.

Heretofore, it usually has been possible to read the time indicated by a portable time piece at night without an exter-nal source of illumination only if the time piece was equippd with the so-called radium dial. In this form of construction a mixture of fluorescent material such as willemite with a small amount of radium or other ra-dio active material to excite the iinorescent material is applied to the hands and chapters of the time piece. The glow of the lluorescent material was thus easily visible to the darli adapted eye.

However, in recent years there has been an ever increasing concern as to possible health hazards to the user because of the presence oi radio active materials in such close proximity to his person for a major portion of every day. It thus becomes desirable to avoid both actual hazard and reputed hazard while still providing the undoubted convenience of being able to read the time in the dark.

Within the past few years, the so-called electronic time pieces have become available. Usually these employ a mechanically resonant element such as a tuning fork or balance wheel electromechanically driven from a battery and mechanically coupled to a reducing gear train which drives the watch hands.

@ne particular form of electron-ic time piece utilizes a tuning fork operating at 360 cycles per second corpled to a transistor in a self oscillatory circuit and to a small battery, all combined within a case auout the size of the usual wrist watch. The tuning fork mechanically operates a pawl coupled to a ratchet wheel. The ratchet wheel has 350i teeth in its periphery and therefore turns at l revolution per second. A 6G to l gear reduction train drives the second hand at l revolution per minute and further conventional gear reduction trains drive the hour and minute hands at respectively 2 revolutions per day and l revolution per hour.

In accordance with the principles of my present invention, a watch as aforesaid is provided with an electroluminescent dial or with electroluminescent chapters or characters and hands on a dark dial, energized by the 360 cycle current derived from the driving circuit for the tuning fork to make the dial and hands visible in the dark.

The present invention will be more fully understood by reference to the following detailed description which iis accompanied by `a drawing in which FIGURE l illustrates diagrammatically an embodiment ot the present invention while FEGURE 2 illustrates in greatly enlarged transverse cross-section a dial suitable for use in my nvention; FlGURE 3 illustrates a modilied form of dial shown in FIGURE 2; FIGURE 4 illustrates a modication of the circuit shown in FIGURE l; while FIGURE 5 is a schematic showing of still a further modification of the circuit arrangement of FIGURE l.

In FIGURE l I have shown a tuning fork lil having permanently magnetized pole pieces l2 and 14 at the ends of the legs of the tuning fork. In inductive relationship to magnet 14 is driving coil 16 and similarly arranged with respect to magnet l2 is feedback winding i8. Driving coil 16 is connected in a circuit running from collector plgfill Patented Mar'. 5, 1953 2l) of transistor 21 through driving coil 16 to battery 22 and thence to base 24 of transistor 21. Pick-up coil 18 is connected in a series circuit running from emitter 26 through pick-rp coil I8, resistor 28 by-passed by capacitor 3d, and thence to base 24. Coils 1.6 and IS are so phased as to maintain oscillation of the mechanically resonant tuning fork l0, preferably at a frequency of 360 cycles. The tuning fork is so constructed as to be insensitive to variations in temperature, so that the time keeping ability of the watch is not aliected by variations in ambient conditions. A light pawl 32 connected to one of the legs of tuning fork llt engages ratchet teeth on driving wheel 34 one tooth at a time for each Vibration of tuning fork lil. A light click pawl 36 bearing against the ratchet teeth on wheel 34 is provided to assure that the wheel 34 is not dragged backwards by the friction of pawl finger 32 in its reverse motion. if wheel 34 has 360 teeth and the tuning forlfL operates at 360 cycles per second, wheel 345 makes l revolution per second. A simple 60:1 gear reduction, as by means of pinion 3S mounted concentrically with wheel 34 and gear wheel el), drives shaft 42 at l revolution per minute and hand i4 therefore constitutes the second han-d of the watch.

rIhe further gear reduction train diagrammatically indicated drives minute hand 46 at l revolution per hour and hour hand d8 at 2 revolutions per day, as is conventional in watch practice.

In the embodiment of the invention illustrated in FIG- URE l, I have provided a secondary coil Sti in inductive relationship to driving coil i6 and having such turns ratio with regard to coil lo as to provide a surTicient voltage to energize the electroluminescent dial 52 of the watch. One connection of coil 5d runs directly to metal base plate S' of dial 52 while the other end of coil Sti is directly connected to a transparent conductivecoating 63 over the face o dial 52. If desired, a switch 5S may be provided in circuit with coil Sli to cie-energize the electroluminescent dial when no illumination is desired.

In the form of watch dial shown in transverse crosssec'tion in FIGURE 2, the metal backing plate 54 of the dial has the chapters or numerals di) of the dial printed thereon with a mixture of an electrolum'inescent phosphor in a glass frit The glass rit preferably has a high dielectric constant. Portions of dial plate S4 which are not occupied by the numerals 6l? are coated with an insulatng layer 62. insulating layer 62 may conveniently be formed of a thin layer of glass frit or enamel with no phosphor embedded in it and preferably of as low a dielectric constant as possible. rIhe use of a low dielectric constant glass for insulation between the dial plate 54 and the transparent conductive coating 63 reduces idle or dead capacity, thus minimizing the capacitive loading on the oscillator circuit. Over at least each of the numerals oil and over a narrow ring-like area around central aperture de is laid down a thin transparent conductive coating 63. It the coating 63 docs not cover the entire dial face, all of the individual transparent conductive coating spots are connected together by narrow transparent coating strips do. Alternating current produced in coil Sil establishes a varying electric field across the embedded phosphor forming each of the numbers and excites the phosphor to luminescence whereby the numbers are caused to glow so that they may readily be distinguished in the darkness.

in order to read the positions of at least the hour and minute hands with respect to the numbers, said hands are each made or" a thin, metal strip lil coated on the face with a dielectric layer 72 containing electroluminescent phosphor with a thin transparent conductive coating 74 overall. A thin, conductive washer or slip ring 75 coaxial with the mounting hub 7S for each oi the hands is secured to the back surface of the hand with an insulating washer '3 Si) intervening and having a conductive connection 82 to the transparent conductive coating on the face of the hand. A thin circular leaf spring 84 secured to the con-V ductive coating 60 on the watch dial, by means of a conductive adhesive or solder, bears against conductive washer 76 on the backl of the hour hand and completes an energizing circuit Vfor the electroluminescent hour hand. Another spring ed is conduc'tively secured to the transparent conductive coating'M on the face lof the hour hand to bear against a slip'ring 76 on the minute hand. The return Aside of the circuit is, for both hands, completed through conductive connection of the hands lto the shaft on which hour wheel 9rd and cannon pinion 92 are individually mounted.

The modified dial shown in enlarged fragmentary crosssection in FIGURE 3v utilizes a continu-ous electroluminescentV layer 166 covering the entire face surface of dial plate 54,. As in the previous embodiment the electroluminescent layer is preferably composed of a mixture of glass frit land phosphor fired -o-n the surface of the dial plate. Under some circumstances however it may be desirable to utilize an organic plastic dielectric rather than a glass frit.

The electroluminescent layer 106 is coated with a con-V tinuous transparent conduct-ive' layer lltiS having opaque numerals printed on the surface, one being indicated at 119. Whilethe hands are not shown in this view, they are the usual opaque hands as used on conventional time pieces. Since the entire face glows when coil '50 is connected from plate 54 to coating 10S, the numerals and hands stand tout dark against the lighted background making thetime piece easily read in darkness. Wit-hV this modification particularly, it is desirable to arrange switch 58 to be norm-allyfopen and only lIQclose it when it is desired to read the time. The comparatively large glowing area may bedisturbing if it is continu-ously energized. Furthermore, the load on the oscillator circuit will be larger lthus increasing the battery drain. However, momentary energization of the dial is satisfactory even if the load is suicient to cause the oscillator to be overloaded since such periods will be brief enough and usually infrequent enough that they will not Seriously affect the time keeping qualities of the watch.

Where there is sufficient space within the Watch case and it is desired to vconvert anon-illuminated electric watch to an illuminated one, the modified circuit shown in FIGURE 4 may be used. In-this figure, parts similar to those in FIGURE l bear the same reference numerals and wil-l not again be described. vThe modifications in'- clude a transformer having its primary winding 112 in series betweendriving. coil 16 andI batte-ry 22 with secf ondary winding V114i connected to switch 5S and dial 52 asindicated by the legend. ThisV modification also provides for more freedom in design of the stepup r-atio between the alternating current in the oscillator circuit and lthat utilized to illuminate the dial.

' The further modification shown in FIGURE 5 substitutes the capacitance of the electroluminescent lamp for the condenser 30 of FIGURE l. The capacit-ance of the -lamp is purposely made lossy enough to substitute also for the resistance of resistor 28 of FIGURE l. In this modification, of course, the dial must be energized at yali times since the dial is then an essential element of the oscillator lcircuit for driving timing fork 10 so switch 58 is omitted.

While I- have shown and particularly described several modifications of my invention, it should be understood that my invention is not limited theretoY but modifications within the scope of the appended claims may be made.

l. A portableelectronic time piece including a mechanically"resonant-element, adial and hands, a gear drive coupled to said -resonantclernent andato said hands whereby said hands are driven, an electrical circuit for driving said resonant element from a battery contained within within said time piece, means for deriving `an alternating current from said circuit, said means comprising a-transformer having a low voltagey primary Winding-in said circuit ,and a high voltage'secondary winding, said dial comprising ya conductive back plate atleast partially' covered with a layer including an electroluminescent phosphor suspendedina dielectric solidfand a transparent' conductive film over said layer and connections: f-rom said high voltage secondary windingto said plate and said iilm.

`3. A portable electronic time piece including a me-l chanically resonant element, adial and hands, a gear drive coupled to said resonant element and to saidhands whereby said' hands'are driven, an electrical circuit for driving said resonant element from a battery contained within said time piece, means for deriving an alternating current from said circuit, said means comprising la trans former having a` low voltage primary winding in said circuit anda high voltage secondary winding, said dial corn-v prising a. conductive back plate'atleast partially coveredV with a layer including an electroluminescent phosphor suspended in a transparent dielectric solid and-a transparen't conductive film over said laye-r and 'connections from said high voltage secondary winding to said plateV and said film, said hands comprising conductive base portions coated with an electroluminescent phosphor suspended in a solid dielectric and each having a transparentV conduct-ive film thereover, an electrical connection from each of said supports to said plate and an electrical connection from each of the transparent conductiveifilms on said hands to said conductive film onsaid dial.

4, A portable electronic time piece including a me-t chanically resonant element, a dial and hands, a gear drive coupled to'said resonant element andtosaid hands wherebysaid hands are driven, an` electrical circuitfotf driving saidire'so-n-ant element from a battery'contained within said timepiece, means for deriving an alternating current from said circuit, said means comprising atransformer having a low voltage primary winding in said circuit and a high voltage secondary winding, saiddial having its chapters formed of an electroluminescent phosphor suspended in a transparent dielectricfsolid on-a conductive baseplate, the areas between saidlchapters being coated with a dielectric film, a'transparent conductive film over at least said chapters and connections from said high voltage secondary winding to said base plate and said conductive film. v

5. A portable electronic time piece'including' a mechajnically resonant element, .a dial and hands, a` gear drive coupled to said resonant element and to said hands whereby said hands are driven, an electrical circuit for driving said resonant element froma battery contained within said time piece, means for derivinglari alternating current from said circuit, said dial having its chapters formed of -an electroluminescent phosphor suspended in a transparent dielectric solid on a conductive b-ase plate,` a transparent conductive film over each of said chapters, strips of conductive coating connecting each of the con-l ductive films over Vsaid chapters, connections'from said conductive base plate and saidV conductive coatingto said means, said hands comprising conductive baseportions coated with an electrolurninescent phosphor suspended in aisolid dielectric 'and each havinga'transparent conductive film thereover, an electrical connection from each of said supports to said plate and an electrical connection from each of the transparent conductive tilms on said hands to said conductive film on said di-al.

References Cited in the le of this patent UNITED STATES PATENTS 6 FOREIGN PATENTS Great Britain Nov. 14, 1956 OTHER REFERENCES 5 Electro1urninescence, E. C. Payne et al., Illuminating Engineering, November 1950, pages 688-693.

Now The Atomic Wrist Watch, John Pfeiier, The N.Y. Times Magazine, Sept. 2, 1956, page 23.

Electroluminescence and Its Applications, J. N. Bow- 10 fel, Journal LEE., August 1957.

RCA TN No. 111, Princeton, NJ., April 1, 1958, one page. 

1. A PORTABLE ELECTRONIC TIME PIECE INCLUDING A MECHANICALLY RESONANT ELEMENT, A DIAL AND HANDS, A GEAR DRIVE COUPLED TO SAID RESONANT ELEMENT AND TO SAID HANDS WHEREBY SAID HANDS ARE DRIVEN, AN ELECTRICAL CIRCUIT FOR DRIVING SAID RESONANT ELEMENT FROM A BATTERY CONTAINED WITHIN SAID TIME PIECE, MEANS FOR DERIVING AN ALTERNATING CURRENT FROM SAID CIRCUIT, SAID MEANS COMPRISING A TRANSFORMER HAVING A LOW VOLTAGE PRIMARY WINDING IN SAID CIRCUIT AND A HIGH VOLTAGE SECONDARY WINDING, SAID DIAL INCLUDING AN ELECTROLUMINESCENT LAMP ENERGIZED FROM THE HIGH VOLTAGE SECONDARY WINDING OF SAID TRANSFORMER. 